Individual authentication methods include a method for authenticating an individual by registering a fingerprint, a voiceprint, an iris, and a retina of the individual, or a vein pattern of the back of the individual's hand or the individual's finger, or the like as registered data in advance, and verifying and determining data input at the time of authentication and the registered data. In particular, individual authentication using the vein pattern has recently been focused on due to its high discriminating ability.
For the purpose of improving security of the above-mentioned individual authentication methods, since it is essential to block illegal users attempting to impersonate normal authenticated users, methods for blocking such illegal users have been widely developed (for example, refer to Patent Document 1 and Non-Patent Document 1).